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MG MGB Technical - I think my head is cracked

Been working on the car all day. Little bits and pieces. I cleaned and stripped my dizzy and replaced the plates with some better ones I got from a junk yard (mine were all rusted) and I added on my new pertronix ignitor. Makes the timing a lot more stable. But then I noticed a slight coolant drip above the No. 2 plug. Only very slight. I'd seen it before and cleaned it off thinking it was just run off from when my radiator fan switch blew. But on looking closer I think the head is cracked. I took off the valve cover and I am sure there is a visible crack running up from the plug and across the head. I think it may have been welded before and ground back from the looks of it. So far the engine hasn't been run hard at all so I imagine things would only get worse. Bit heartbreaking really as I am so close to getting the whole car done. Guess I have to save up for a new head now. Bugger :(
Simon Jansen

You might try some ceramic sealant of some kind. There are sealants you can run through the cooling system which will often seal tiny cracks such as the one you are describing.

Sean
Sean Brown

If you can see the crack it is more than tiny. Our 79 was giving us some problems last year, high oil consumption, running warm, difficulty starting, I pulled the head and cleaned it up, it looked perfect but I had it magnafluxed anyway, that showed a crack which was only visible after the shop had put a dye on it to show me where it was.

Have the head magnafluxed, it's cheap enough to make it worth it but be prepared to start hunting for another head.
The Wiz

Simon. There is a tech article on my website, www.custompistols.com/ which describes one procedure for crack checking. It might be of use to you if the test kit is available, to the general public, in NZ.

In my experience, about 80% of the cylinder heads tested, from the "US Spec", actually North American Specification--almost, rubber bumper cars showed cracked cylinder heads when inspected. Unless you need a cylinder head with the ports for the air pump in it, I would suggest that you obtain a used, UK version cylinder head and install it on your car. One of these may be available in either New Zealand or Australia at a significantly lower cost than a new production cylinder head. If not, either Chris Betson or Peter Burgess might be able to provide such a cylinder head.

As a "plug" for Peter, let me say that I rebuilt my 79 engine using an American tuner for the cylinder head and used Peter to build his "Econo-Tune" i.e. his bottom of the line cylinder head, for my daughter's 77B. The actual cost was about the same. I had to ship the cylinder head to Peter and he had to ship it back to me. International shipping is far more expensive than internal shipping. Thus, the "bottom line" costs were about equal. The performance is not. Peter worked with me, the other rebuilder did not. My car works fairly well, but not very much better than a stock cylinder head. Theresa's car blows mine away. In spite of having a slighly lower bore (her's was bored to .020" over while mine was bored to .040" over) her car, using the same carbs, will outperform mine. Quite clearly--as she has demonstrated.

Contact Chris or Peter if you cannot find a cylinder head locally. Having dealt with both of them, over several years, I am sure that they will do their best to help you. Both of them help to define the term "Enthusiast".

Drove my daughter's car today. Had a problem with the alternator, which we, finally, got resolved. (The Autolite rebuild no longer has the connector pattern that was used on the 77B, only those used on the later model cars. Moss is sending out the newer style plug in connection which should correct the problem for all time.) Could not believe how much better it ran than my own 79 LE. This is, once again, with the American tuner's cylinder head vs. Peter's bottom of the line cylinder head.

If the money is available, consider having Peter send you a later model cylinder head modifed to the "Econo-Tune" specification. Should not cost much more than a brand new cylinder head, but the difference is performance has to be seen to be appreciated.

Les
Les Bengtson

What a bu88er.

Look out for a 1800 Land Crab head, there still could be some around.

If you really get stuck, I have one with new exhaust inserts that you can borrow - (needs assembly though...)

Ian F

Ian Fraser

Don't panic yet!

If the weep is small then there is a possible fix.

Clean the area around the weep to around 1/2 inch diameter with a small grinding stone , leaving it quite rough.

Apply a layer of Araldite or JB weld over the whole area and leave to set a couple of days.

The casting at this point is quite thin and other types of repair, such as stitching are rarely successful.

It may sound like a bodge but it works - I have had fixes like this hold up for several years.

At least it will buy you time to find a replacement at your leisure.

Chris at Octarine Services


Don't be afraid, this out side craking is not that
dangerous, one friend of mine has been driving a car with such a crack since some years without problem. The main issue with head cracks comes from an internal one either between two valve seats ig.
I own Three heads from stock and all three start cracking in the middle main water way to block and from my own it's a casting default as all have a non continuous thickness in this area. One had been previously repaired as I can see two small inserts. New heads are less prone to crack because of a higher quality cast metal and casting process too.
Renou

It's a bit hard to see but I put a picture up:

http://www.asciimation.co.nz/pics/page9.html
Simon Jansen

Simon, not to change the subject, but put a dab of RTV sealant under the magnetic trigger for your ignition if you haven't already. The Pertronix trigger can turn on the points cam, allowing your timing to vary.

Sorry to hear about the leak! Best of luck on that!
Jeff Schlemmer

Simon,

The picture is telling so much. Mine of friend B head is cracked in that exact place too. But he ran twice the Monte Carlo Classic with this problem . Unfortunatly,
this location is stated as proned to cracks. Even P.Burgess tells that story, see page 20 in his book, a double cracked head each side of the head nut pilard towards plug #2 and #3.
Renou

Hi Simon, maybe you need this...
auction number 4616783578 on eBay, new alloy head and reasonable shipping price to NZ :)
Just a thought!
James Finlayson

Bad luck, but it seems Chris has the answer.

Did you empty that case of Corona as a result? Must be awfully expensive down there.
Edd Weninger

Edd, at one point I had most of that MG stored in empty Corona boxes!

James, that head works out to be very reasonable actually in NZ dollars (even counting GST). And I suspect cheaper than getting a normal cast one locally. That is my job for today, to call around and find options.

Renou, I have that book so I looked it up and you're right. Peter says in this case the head is scrap.

And Jeff, thanks for the tip. I will do that tonight when I get home.

Chris, wouldn't Araldite not stand the head there. I thought it was only good up to 60C? Never seen JB weld locally. Always wanted to get some to play with.

What si the danger with running the engine with such a crack? Just that it will leak and eventually get worse and I lose compression and get water in the oil? The problem is that now I know it is there it will bug the hell out of me until it is fixed.
Simon Jansen

Simon,

Araldite seems to hold up just fine - in fact if you heat up the casting first the glue will melt and become glass like.

I have even used it to glue together an oil line running at 100 + C and 80 psi - it held for years.

There are specific high temperature epoxies, both straight and metal filled - a search of the web should find a local supplier.
Chris at Octarine Services

Simon,

No-Risk at all but the crack may enlarge on time. Chris advice sounds quite relevant and not that much expensive. Another one had been told me by a NEYRPIC engeneer: you melt the white egg part into the coolant. when wipping, it happens to lock the leack. My friend did two Monte Carlo classics with his GT and such a cracked head with no more problem. But any way, that let you time to get a spare head.
Renou

I noticed some coolant around either my number 1 or 2 spark plug on my car. I was changing the water pump at the time so I assumed it had splashed there. Maybe I should take a closer look. I hope its just a splash.
andrew.horrocks

I had a crack in my head, and used the araldite leakfix stuff and the car ran fine for a seasons racing!

Tony
Tony

"Edd, at one point I had most of that MG stored in empty Corona boxes!"

Interesting image, you're drinking the Corona rapidly enough to have enough boxes as you disasswmble the MGB" He he...
Edd Weninger

An awful lot of blood, sweat and beers have gone into that car so far!

I think I am going to get a new bare unleaded head and I will transfer across my valves and valve gear from the old one since all that was new when I rebuilt the engine. The new head is about $1000NZ.

I am also thinking since I will be running unleaded I can add in the O2 sensor kit I have to measure the mixture. Be a handy tuning tool. Where is the best place to add the sensor. Can you carefully drill and tap the cast manifold to add one?
Simon Jansen

Most O2 sensor installations I have seen have a "bung" welded into the down pipe to accept the sensor and not tapped into the manifold. Make it in a convenient place to have easy access.

I understand that there is a bottle deposit on Corona bottles. If you ship them back to Mexico, you might get $0.02 per bottle.
Edd Weninger

Simon, add the O2 sensor just below the manifold. You risk cracking the manifold if you try to drill and tap it. Besides, its not really thick enough to get adequate threads tapped, and there is not flat spot to seat the sensor. You can weld the bung in now, but put a few hundred miles on the engine before you install the sensor. If you don't get the rings seated first, the excess oil in your exhaust will ruin the sensor and you're out $75. You are right though, its a tremendous tuning tool!!!
Jeff Schlemmer

OK, thanks guys. Will look into that but no rush. Besides I need to assemble the little kit for the display first!
Simon Jansen

Simon,


Please have a look at the following URL:
"http://www.piercemanifolds.com/cylinderheads.htm"
A brand new cast alloy head with bronze guides and reinforced valve seats. You too may ask for a VAT detax
for export. But I don't know any more about these products. Any advice welcome please.
Renou

Renou, I am getting my new head sourced locally. My parts guy can get me a secondhand head, crack tested (the bit I missed last time), machined with new hardened seats installed, new valve guides, and all new valves properly faced and ready to go. I will just put my old rocker gear (which is actually new rocker gear) onto it. I will just burette the chambers and clean them up to get rid of any rough spots. Will take a lot less time than getting one from overseas and even though I don't have to pay VAT you sometimes do end up paying extra duty when you bring things into NZ.

The crossflow heads look nice though :)
Simon Jansen

This thread was discussed between 25/02/2006 and 28/02/2006

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